Electric lamp



y 1933- G. v. DOWNEF 2,116,722

ELECTRIC LAMP Filed Oct. '5, 1935 Patented May 10, 1938 UNITED STATESPATENT OFFICE Application October 5, 1935, Serial No. 43,757 In GreatBritain October 8, 1934 1 Claim.

This invention relates to electric lamps and its object is to provide alamp in which excessive intensity of the light in certain directions isminimized with a view to improving the general distribution of thelight.

Another object is to increase the light given out in certain directionswhere it is most useful.

With this object in view the invention consists in an electric lamp inwhich the wall of the bulb is indented'towards the luminous element inan area where the radiation is stronger than necessary for optimumdistribution, the sides of the indentation being formed at such an angleas to reduce the amount of light passing directly therethrough byreflecting some of it in other and more useful directions.

The invention is particularly applicable to the type of electric lamp inwhich the luminous element consists of a filament which is bent orcurved in one plane, for example, in the form of a part circle orpolygon in a horizontal plane, in which case more light is radiated inthe plane of the filament than in other directions, and a bright line orband is liable to be thrown on the walls or on adjacent objects in theplane of the filament, and in the case of a horizontal filament mostlight is radiated in the least useful direction, i. e. in a horizontalplane.

In this case the excess radiation in the plane of the filament isreduced in accordance with the invention by forming the indentationpartly or wholly around the bulb adjacent the filament and in or nearthe plane thereof, whereby some of the horizontal radiation is reflectedupwards and/or downwards by the walls of the indentation.

The invention is illustrated by way of example in the accompanyingdrawing, in which Fig. 1 shows partly in section an electric lamp inaccordance with the invention, and

Fig. 2 shows a modification.

Referring to the drawing, the glass bulb I of the lamp shown in Fig. 1is formed with an indentation 4 opposite and surrounding the filament 3,the apex of the indentation being approximately in the plane of thefilament. Owing to the acute angle of incidence of the light on thesides of the indentation 4 a considerable proportion of the light willbe reflected upwardly or downwardly as shown by the dotted lines andconsiderably less light will be directly transmitted horizontally, thusreducing the illumination in and near the plane of the filament andincreasing the illumination of the working plane below the lamp and ofthe ceiling above the lamp.

In the modification shown in Fig. 2 a diffusing band 2 is formed on theglass wall of the bulb in the area of indentation, whereby the amount oflight directly transmitted through the indented part of the bulb isfurther reduced by absorption and the amount reflected upwardly ordownwardly from the sides of the indentation 4 is increased by therelative opacity of the glass. The diffusing band 2 is preferably, butnot necessarily, graduated at its edges as shown, to avoid any suddenchanges in the intensity of the illumination of different areas.

The apex of indentation need not be exactly in the plane of thefilament. For instance if it is desired to increase the amount of lightrefiected downwardly and to decrease relatively the amount of lightthrown upwardly on to the ceiling, the deflecting indentation might beformed with its apex slightly above or behind the plane of the filament.Alternatively the upper and lower sides of the indentation might beformed at different angles to the plane of the filament.

It will be obvious that the dimensions and proportions of theindentation may vary widely according to the circumstances.

What I claim is:-

An electric lamp having a luminous element and a transparent bulbenclosing said luminous element, said bulb being formed with anindentation of substantially V-shape in cross section longitudinally ofthe bulb, the apex of the inner face of said indentation being sopositioned with respect to said luminous element as to be located in thezone of the greatest intensity of illumination from said luminouselement when the same is rendered luminous by an electric current.

GEORGE VICTOR DOWNER.

